It has heretofore been generally known in the food industry, and in particular in the citrus industry, to print or stamp identifying names as well as other indicia on objects, food products, citrus fruits and the like.
A variety of commercially available printing machines have been developed for commercial use, and by means of which the stamping or printing is made possible on a continuous high speed basis. For example, the machine as disclosed in the Johnson, Jr. et al U. S. Pat. No. 2,987,991 is characteristic, and is incorporated into the present disclosure by reference.
Briefly, the machine of this patent includes a continuous conveyor with a plurality of spaced rotatable rollers capable of orienting and aligning fruits, vegetables, or other ellipsoidally shaped articles or objects so that their long axes are parallel to the axes of the rollers. The conveyor conducts the fruits or objects successively to a position between a rotary printing drum and underlying rotary platens, where inked printing dies apply ink indicium to the fruit or objects, which are then moved through a delivery path to an appropriate receiver.
It has been discovered that the type of printing ink which is used is an important consideration, particularly due to the commercial handling methods in which citrus fruits are stored at low temperatures (40.degree.-55.degree. F.) and high humidity (90% RH). When such fruit is packed, transported and displayed, it is commonly subjected to both high and low temperatures. Thus, when the cold fruit is exposed to warm, moist air, its temperature is below the dew point, and water tends to collect on the surface of the fruit. This condition, which is described as "sweating", is a normal effect in the industry and may vary from a light film of moisture to more copious amounts of condensate. In order to cope with this condition, the printing inks commonly employed are of the water non-soluble type so that the printed indicia remains "fast" and does not run or smear under the above described conditions.
More recently, however, although many of the present inks are safe and acceptable in most countries, new and increasingly more stringent food laws have been enacted in certain localities of the world, which prohibit the use of such water non-soluble types of inks, and require that all substances applied to food items should, in general, be a food grade, that is, fit for human consumption. Since the previously used water non-soluble inks do not always qualify under the new food regulations, it has been necessary to formulate new stamping or printing ink.
In developing such an ink, it has been discovered that the only dyes that are presently available for the formulation of an acceptable ink have relatively high water solubility and low oil solubility characteristics. Such inks, therefore, present serious problems with respect to the attainment of a desired sufficiently high tinctorial strength and sweat resistance.
To overcome the above noted problems, the present invention proposes an improved printing concept in which an acceptable ink is utilized in the printing machine for the printing or stamping of the indicium on the fruit, and wherein the stamped fruit will be delivered via a delivery path to the receiver, and while the fruit is in such delivery path apply a quick drying, transparent protective sealed coating to the indicium area. In this manner, the ink indicium will be sealed so that it will not run or smear, when subjected to the moisture and sweat producing conditions, and will continue to remain clear and legible.